13,275 research outputs found
Contact-eutectic-lens fabrication technique
Method enables use of crystal or semiconductor materials with selective spectral-response characteristics (ultraviolet, visible, or infrared wavelengths) in fabrication of contact lenses, reading glasses, and photographic processing equipment
Supersolidity and phase diagram of softcore bosons in a triangular lattice
We study the softcore extended Bose Hubbard model in a two-dimensional
triangular lattice by using the quantum Monte Carlo methods. The ground state
phase diagram of the system exhibits a very fruitful structure. Except the Mott
insulating state, four kinds of solid states with respect to the commensurate
filling factors and are identified. Two of them (CDW II
and CDW III) are newly predicted. In incommensurate fillings, superfluid,
spuersolid as well as phase separation states are detected . As in the case for
the hardcore bosons, a supersolid phase exists in while it is
unstable towards the phase separation in . However, this instability
is refrained in due to the softening of the bosons and then a
supersolid phase survives.Comment: 4 pages, 5 figure
Zero-gravity growth of NaF-NaCl eutectics in the NASA Skylab program
Continuous and discontinuous NaF fibers, embedded in a NaCl matrix, were produced in space and on earth. The production of continuous fibers in a eutectic mixture is attributed to the absence of convection current in the liquid during solidification in space. Image transmission and optical transmittance measurements of transverse sections of the space-grown and earth-grown ingots were made with a light microscope and a spectrometer. It is shown that better optical properties were obtained from samples grown in space. This was attributed to a better alignment of NaF fibers along the ingot axis. A new concept is advanced to explain the phenomenon of transmittance versus far infrared wavelength of the directionally solidified NaCl-NaF eutectic in terms of the two-dimensional Bragg Scattering and the polarization effect of Rayleigh scattering. This concept can be applied to other eutectic systems as long as the index of refraction of the matrix over a range of wavelengths is known. Experimental data are in agreement with the theoretical prediction
Nanocrystalline iron at high pressure
X-ray diffraction measurements were performed on nanocrystalline iron up to 46 GPa. For nanocrystalline epsilon-Fe, analysis of lattice parameter data provides a bulk modulus, K, of 179±8 GPa and a pressure derivative of the bulk modulus, K[prime], of 3.6±0.7, similar to the large-grained control sample. The extrapolated zero-pressure unit cell volume of nanocrystalline epsilon-Fe is 22.9±0.2 Å^3, compared to 22.3±0.2 Å^3 for large-grained epsilon-Fe. No significant grain growth was observed to occur under pressure
Vibrations of micro-eV energies in nanocrystalline microstructures
The phonon density of states of nanocrystalline bcc Fe and nanocrystalline fcc Ni3Fe were measured by inelastic neutron scattering in two different ranges of energy. As has been reported previously, the nanocrystalline materials showed enhancements in their phonon density of states at energies from 2 to 15 meV, compared to control samples composed of large crystals. The present measurements were extended to energies in the micro-eV range, and showed significant, but smaller, enhancements in the number of modes in the energy range from 5 to 18 mueV. These modes of micro-eV energies provide a long-wavelength limit that bounds the fraction of modes at milli-eV energies originating with the cooperative dynamics of the nanocrystalline microstructure
CP Measurement in Quantum Teleportation of Neutral Mesons
Quantum teleportation using neutral pseudoscalar mesons shows novel
connections between particle physics and quantum information. The projection
basis, which is crucial in the teleportation process, is determined by the
conservation laws of particle physics, and is different from the Bell basis, as
in the usual case. Here we show that one can verify the teleportation process
by CP measurement. This method significantly simplifies the high energy quantum
teleportation protocol. Especially, it is rigorous, and is independent of
whether CP is violated in weak decays. This method can also be applied to
general verification of Einstein-Podolsky-Rosen correlations in particle
physics.Comment: 7 page
A gapless charge mode induced by the boundary states in the half-filled Hubbard open-chain
We discuss the ground state and some excited states of the half-filled
Hubbard model defined on an open chain with L sites, where only one of the
boundary sites has a different value of chemical potential. We consider the
case when the boundary site has a negative chemical potential -p and the
Hubbard coupling U is positive. By an analytic method we show that when p is
larger than the transfer integral some of the ground-state solutions of the
Bethe ansatz equations become complex-valued. It follows that there is a
``surface phase transition'' at some critical value p_c; when p<p_c all the
charge excitations have the gap for the half-filled band, while there exists a
massless charge mode when p>p_c.Comment: Revtex, 25 pages, 3 eps figures; Full revision with Appendixes adde
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